1. Field of the Invention
The present invention relates to a television lens of a photo-taking apparatus such as a television camera, and more particularly to a lens barrel arranged to prevent erroneous operations.
2. Description of the Related Art
A device for driving optical means by transmitting a driving force from driving means to manual operation means through magnetic coupling means has been disclosed in Japanese Laid-Open Patent Application No. Hei 9-138335 (corresponding to U.S. Pat. No. 5,731,919).
FIG. 12 shows the device disclosed in the above-cited patent application, the details of which are omitted from the description herein. In brief, the device is arranged to transmit the rotation of a rotor 81 of a driving motor to a manual operation ring 84 through a slipping surface of a thin plate 82 which is coupled with a magnet 83 by a magnetic force generated between them. In carrying out a motor driving operation, the manual ring 84 is rotated by the motor to move optical moving means held inside the device.
In the case of manual operation, a large holding force of the motor permits the manual ring 84 to slip at the magnetic coupling part so as to move only the manual ring 84 and the optical means internally coupled with the manual ring 84.
An advantage of the device described above, as an example of the prior art, lies in that the device enables the user of the photo-taking apparatus to freely select either a motor driving operation or a manual operation without performing any additional operation for switching between the motor driving operation and the manual operation.
However, it has been a problem with the prior art example that, if a unit or an operation part provided for the motor driving operation is inadvertently touched by the user during manual operation, movement of the optical means under the manual operation would be affected by the inadvertent touch, because it instantly renders the motor driving operation possible.
This drawback occurs particularly in cases where the above-stated arrangement is applied to television (TV) zoom lenses for zoom driving, including, of course, such a television zoom lens that uses a dedicated operation accessory. FIGS. 13 and 14 illustrate such an arrangement including a TV camera, a TV lens, and a zoom operation switch 88 for a motor driving operation disposed at a position where it is readily operable, i.e., readily touchable, on a lens grip 87, which is generally provided for holding the camera 85 and the lens 86. Therefore, although the above-cited prior art arrangement, which obviates the necessity for any additional operation for switch-over, excels in operability, use of it for driving the lens of such a TV camera tends to cause a motor driving operation to be inadvertently performed while a manual operation is in process.
It is an object of the present invention to overcome the above-mentioned problems and to provide a lens barrel or a photo-taking apparatus which has a setting switch arranged to prevent any erroneous operation from being unintentionally performed by the user thereof, and which excels in safety and the like.
To attain the above object, in accordance with an aspect of the present invention, there is provided a lens barrel, which comprises an optical lens unit, a manual operation member for manually moving the optical lens unit in an optical axis direction, a motor member for driving the optical lens unit in the optical axis direction, a motor operation member for actuating the motor member, the motor operation member being arranged to output a signal relating to an operation of the motor operation member, and the motor member being arranged to be driven according to the signal, a transmission mechanism capable of driving the optical lens unit in the optical axis direction by concurrently transmitting an operation force of the manual operation member and a driving force of the motor member to the optical lens unit, and a setting member for setting the motor member into an inoperative state.
In particular, in the lens barrel, the setting member is arranged to cut off a supply of electric power to the motor member.
Further, in the lens barrel, the setting member is arranged to bring the signal relating to the operation into an off-state.
Further, in the lens barrel, the motor operation member is arranged to output a signal corresponding to an amount of operation of the motor operation member.
Further, in the lens barrel, the motor operation member is a seesaw-type switch.
Further, in the lens barrel, the motor member is arranged to drive the manual operation member.
In accordance with another aspect of the invention, there is provided a lens barrel, which comprises an optical lens unit, a manual operation member for manually moving the optical lens unit in an optical axis direction, a motor member for driving the optical lens unit in the optical axis direction, a motor operation member for actuating the motor member, the motor operation member being arranged to output a signal relating to an operation of the motor operation member, and the motor member being arranged to be driven according to the signal, a transmission mechanism for transmitting a driving force of the motor member to the optical lens unit, determination means for determining, on the basis of the signal relating to the operation, whether the motor operation member is being operated or not, cut-off means for cutting off transmission of the driving force of the motor member by the transmission mechanism if the determination means determines that the motor operation member is not being operated, and a setting member for setting the motor member into an inoperative state.
In particular, in the lens barrel, the cut-off means is a clutch mechanism.
Further, in the lens barrel, the motor operation member is provided on a lens grip disposed at the lens barrel.
Further, the lens barrel is a television lens barrel.